1. Field of the Invention
The invention relates generally to digital communication units, and more particularly, to a unit and method for managing the communication charge of communication units that carry out digital communication using the Integrated Services Digital Network (ISDN) line.
2. Description of Background Art
Various non-telephone in-house equipments such as facsimile machines and personal computers, in addition to telephone sets, are being connected to common subscriber line widely used in the progress in the tele-communication technology.
Meanwhile, digitalization in transmission media and branch exchangers is advanced in accordance with the development of digital technology.
Under such circumstances, a digital communication network called ISDN is being developed to provide various services of telephones and non-telephones integratedly by a digital network that couples various digital equipments. ISDN is appreciated to be a service network "comprising functions for providing digital connection between users and the network interface" in the description hereinafter.
In the case of telecommunication using a digital communication network such as ISDN, details of the transmitting destination, the transmitting date and time, the transmitting time period, etc. are recorded by a center every subscriber line. However, only the communication charge is notified to an user at the end of communication so that the user is only aware of the communication charge of that time. The details of the communication charge on a month basis is reported to the user in the form of a bill from the telecommunication company. These details do not include the classification of in-house terminals, individual users, and communication modes.
In general, the terminal units such as telephone sets and facsimile machines connected to one subscriber line are utilized commonly by many people in the digital communication network. Also, a plurality of terminal equipments including telephone sets and facsimile machines are connected to one subscriber line generally.
In conventional communication network charge management system, an user could not identify the communication charge in an individual basis or a terminal equipment basis, so tracking of details concerning the usage of the terminal equipments was impossible.
In the digital communication network, the communication charge differs depending upon the communication mode, such as communication by telephone, and by G3 mode or G4 mode of the facsimile. However, the user could not track the communication charge independently and separately for respective communication modes in conventional communication network.
A unit for monitoring the communication charge on an ID code basis by specifying the user by an ID code is disclosed in Japanese Patent Laying-Open No. 57-25763. This charge management unit of the prior art comprises a unit that switches a terminal equipment into an usable state in response to application of a registered ID code, a unit that calculates the communication rate or the communication charge on a fixed time period basis that corresponds to the communicating destination in response to the commencement of a communication, a memory for storing communication charge or communication rate for each ID code, and an unit for writing accumulatively the calculated communication charge or the communication rate into the memory region corresponding to the current ID code.